


No Rest for the Wicked

by TheLostOne88



Category: Monster Girl Encyclopedia, Undertale (Video Game)
Genre: Alternate Universe - Underswap (Undertale), Consensual Somnophilia, Ecto-Genitalia (Undertale), F/M, Fuck Yeah Monster girls!!!, Shameless Smut, The reader is a succubus, Underswap Sans (Undertale), also, the kink is somnophilia, the whole damn thing is, we get to see Sans be a sinnamon roll again.
Language: English
Status: Completed
Published: 2019-04-02
Updated: 2019-04-02
Packaged: 2019-12-31 22:42:26
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,768
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18323432
Author URL: https://archiveofourown.org/users/TheLostOne88/pseuds/TheLostOne88
Summary: When the sibling is away a pseudo-innocent skeleton and his succubus girlfriend will play. You were looking forward to a whole weekend of relaxation. It soon takes a turn when a certain one of you finds out the other sleepwalks. What could possibly go wrong?





	No Rest for the Wicked

**Author's Note:**

  * For [Wolfgirl99](https://archiveofourown.org/users/Wolfgirl99/gifts).



> This story is pure smutty goodness, so sinners rejoice and thank Wolfgirl99 for requesting this. We get to explore a kink of mine. Cause who doesn't love sleepy readers and their horny S/O's.
> 
> I do and so will you.  
> Now on to the story, *Rides off on G's back.*

No Rest for the Wicked

 

It was a balmy evening where you were. You had just got off a grueling shift at work. Your boss, a bitch with an ego the size of the planet, really rode your ass today with the errands and work. Nothing you can't handle, but you were glad the weekend was here. You were ready to relax with your favorite two monsters- The Skelebros, Sans and Papyrus. You reached their house and pulled into their driveway.  They lived in a quiet piece of suburb that was mixed with humans and monsters. The brothers also lived in a nice two-story brick house. The reason you decided to come over was that Sans was going to be alone in the house while Papyrus went out of town. The reason he couldn’t disclose. So you and Sans thought about a date night indoors was a nice change of pace. What thrilled you was the idea of being alone again with Sans since you both started going out. The living room and kitchen lights were on, indicating that someone was definitely home. You shuffled out of your car and headed to the door.

 

You barely got on the porch when the door swung open. “YOU’VE ARRIVED!” Sans greeted you with a wide grin and stars in his eyes. He lifts you up and spins you both around. Accustomed to this greeting, you just laugh it off. You loved being greeted so warmly. Then again, Sans always greeted you warmly ever since you guys became friends and then lovers.

 

Your tail shifts from side to side, “I’m home.” Sans leads you in with a gentle hand to your back. He was always protective of you, well, both brothers were like that. Sans was just more prevalent. Once inside the smell of cooked meat and cheese wafted around you. “Mmm is that tacos I smell?” You kick off your shoes and go into the living room. A gasp left you when saw the living room. The couch was pushed back to make room for the elaborate pillow fort. Fairy lights lined the inside and bathed it in a cool blue. Every pillow seemed to be in there. Plus it was big enough to fit four people. “No way, Blue you did this?”

 

The sight of your physical excitement egging him on, he says, “WELL, I FIGURED YOU’D NEEDED SOMETHING FUN AFTER WORK.” Sans said coming in, “SO I, THE MAGNIFICENT SANS, CRAFTED THIS FORT, MWEH HEH HEH HEH!” You gave the fort another look. The inside looked soft and inviting you wanted to get in immediately.

 

“This is great Sans, let me shower first and then I’ll eat okay?”

 

Sans nodded, “TAKE ALL THE TIME YOU NEED. I’M NOT GOING ANYWHERE!” You march upstairs and quickly grab something comfy to wear and jump in the shower. Once in, the tension in your muscles seemed to melt away. “Haaah~ so nice,” you swoon. Who would have thought working for a high-end fashion magazine was hard work? You wallow in the warm water for a few minutes before scrubbing yourself clean. Once you had finished you got dressed and headed back down. True to his word, your Blueberry was waiting for you. The food was now on two decorative placemats, waiting warmly for you to dig in. Sans sat in the fort, sifting through the options of Netflix.

 

You stood by and waited but your eyes drifted to him. You’ve been going out for some time now. You won Papyrus’ approval, and everything was fine. Sort of. You two haven’t quite yet pushed pass the boundary of skinship just yet. You'd think after doing it finally would resolve your shyness, but with life seemed to cockblock you at every turn afterward. Especially from your collective group of friends. They always had a way to eavesdrop or butt in right when you and Sans got to the good part. It didn’t help that Papyrus teased you when he finds out about your pitfalls. _“Sorry Sis, but my bro tells me everything.”_   You mentally curse the taller one.

Jeez, and you call yourself a succubus. This was your base instincts. Charming others and feeding from them are who you are, yet you were a wimp. You loved your blueberry, you really did, but the growing unease and hunger were threatening you to go on a frenzy. Your normal eating wasn’t going to cut it sooner or later.

If only you could have another taste…

“...[y/n]?”

“...”

“HELLO, EARTH TO [Y/N] ARE YOU THERE?” You snapped out of it and looked around. Once you saw that you were indeed in the living room, you apologized. Sans shook his head, “No worries my dear Buttercup, it’s okay. I found the last episode, you ready?” You nodded yes and the night continued on just like that. You watched about four episodes before the exhaustion got to you. 

Normally it’s Sans who fell asleep, but he managed to make it to 2 AM. “Work must have been crazy today,” Sans says as he pulls the blanket over your sleeping form. “Luckily we have all weekend to catch up.” Sans takes your plates and proceeds to go wash them and clean up anything else in the kitchen. Satisfied when his, once again, sparkling kitchen, Sans turned to see a light shadow standing in the doorway. "MWEH!"

It was you.

"Wowzers [y/n] you startled me," Sans relaxed his stance. He walked over to you and saw that you were oddly silent. In the dark, your eyes were glowing that hazy purple color that Sans knew so well. The skeleton eased over to you, "Uuuuh? [y/n] are you ok, say something." slowly taking you in. You swayed a bit and your eyes didn’t seem focused on anything or him for that matter. San pulls you closer, your body goes a bit limp in his arms. "WHOA, [Y/N] ARE YOU OKAY?" You still remain unresponsive. He waves a hand in front of your face and you don’t react Sans began to worry and thought to call Undyne or maybe Papyrus when it dawned on him. He started to laugh a bit,  “[y/n]...are you *snicker* sleepwalking?” Sans has heard of this in humans, but monsters never. Then again you weren't a normal type of monster. Sans takes you back into the blankets of the fort. You easily shut your eyes and Sans goes to turn the T.V. off and sees you sit up. “WH-” Sans covers his mouth. He rather not startle you, “Did I wake you?”

You don’t respond, of course, for a few minutes as a lopsided smile graces your features. The look in your eyes turned predatory and mischievous. ‘Is this what humans call _deja vu_?’

Your tail whips from side to side as you crawl towards him. He scuttles backward, trapped by your body and the TV stand. “Let’s play~” You wrap your arms around him. He looks into your hazy purple eyes before your lips touch his teeth in a clumsy manner. The sensation of your magic caressing his soul came. It fumbled to dominate him, make him submit and throw him into heat. The fact you could do this without being fully awake was amazing, but he expected no less from his datemate.

The force of your magic soon won out. Something told Sans that engaging might be wrong though. He used his magic to guide you back to the fort, where he laid you flat against the pillows. Sans’ soul thumps wildly. The magic warms his bones and he feels his own hard-on growing in his pajama bottoms. He shook his head and forced himself to focus on you. Your body was still heavy with sleep but you muttered your unconscious, horny desires to him. “[y/n]...” he called, “Can you...hear me?”

A slurred version of his name is all he gets as you relaxed into the pillows. Your body squirms as you dream, the top you wore shifting up and exposing your belly.

Sans gulped, your body was vulnerable and underneath him. He had you all to himself. He looked back at your exposed belly. His phalanges kneaded the peeking fleshly gently.

‘Mine…all mine.’

Before he could stop himself, he dipped down to slowly pepper your belly with kisses. A light gasp and a shiver are all he gets, but no other movements. Feeling emboldened by this chance. Sans tugs of the shorts you wore. To his surprise, you weren’t wearing underwear. With a cheeky smile, he spreads your legs. “Look at you, it’s almost like you wanted this to happen.” He gives your thigh a small kiss and then a lick, testing your reaction. You still don’t move or stir. “It’s okay, I like your boldness.” He gets closer to your center and gives it a kiss as well, then a long lick from bottom to the top.

You moaned once again, this time breathlessly saying his name as you pushed your lower half closer to the source of friction. Sans froze as he watched you arched your back, begging for his touch. The fire of his soul grew and he soon quickened his pace. Licking and sucking on your core with wild abandon. He could feel your arousal making you wetter by the second. You squirmed and keened in your sleep, but Sans held on to you. “We’re far from finished Buttercup.” He pushed his skull further into your warm, wet cunt. Your walls fluttered quickly around him before they began to squeeze around his glowing tongue. You tasted heavenly, just like he thought you would. The living room was filled with the sloppy noises of Sans enjoying his time between your legs. He kept his eyes on your twitching form as moans tumbled from your sleepy mouth.

Sans sat up and admired the sight of your body. You mindlessly struggled between sleep and the waking world. He sighed contently as you came down. He gently shushed you before going back to work. Now that you were nice and slick, he didn’t have to worry about hurting you. Sans undoes his bottoms to reveal his rock solid cock. The light from it, an iridescent glow, was all that filled the fort. Before he lines himself up, he pushes your thin shirt up to show your breasts. Your nipples were peaked and begging to be toyed with, which Sans obliged by taking a moment to lick and nibble on one of the sensitive buds. He pinches the other, making you moan again. “One time wasn’t enough for you was it, [y/n]?” he says between licks. “I agree, once isn’t enough for me. I want you wrapped around me as I fuck you into oblivion. I want to see you come undone and only screaming my name.” He bucked his hips, letting his cock get covered in your juices. “You want that too, don’t you Buttercup?”

You said nothing as he grinds into your hips. A low growl came out that he quickly muted by kissing your neck. Careful not to bite down like he wanted to. "Fuck, what I would give to really make you mine, but baby steps as they say."  Sans takes one of your legs and hoists it over his shoulder. Once he was aligned with your entrance, he eased it himself inside. The combination of heat and wetness was enough to drive him wild. His tongue quickly formed, hanging loosely from his mouth as he tried to refocus. “StaaarrRRRsss~ You feel so good, mn.” He rolled his hips and tried to keep a steady pace that wouldn’t, hopefully, wake you.

“Look at you, my Buttercup, so cute and sexy at the same time.” He hisses, “You’ve driven me mad since the day I met you, I knew I wanted you from the beginning.” His pace quickens enough to make your breast move. Oh, how he loved you and how he wanted to wake you up. He needed to hear you moan again. The high keening, the way you squirmed, and how you clawed at his vertebrae as you both chased a climax together.

Ever since he saw you that day in the flower shop, all he ever wanted was you. He wanted to mark you up and down. Let everyone know who’s mate you were. Who truly won the succubus’ heart. He didn’t care what you were, you were perfect and everyone could see that. Anyone who came to take you away wouldn’t stand a chance.

You. Were. His. And. His. ALONE!

Sans could feel his release growing with each contraction of your walls. His thrust got sloppier and sloppier as he hit a spot that seemed to push you closer as well. A good flush had built itself on your skin even as you slept. If this happened again. He was definitely going for it. You just felt so...amazing.

Sans soon let go of your leg and was now face to face with you. His arms at either side of your head and thrusting deep into you faster than before. “Fuuuck, I’m so close.” His tongue lulling out as he focused on reaching his end. You had started to rouse for real this time but groggily said his name. He shushed you and told you not to worry. Dazed by what was going on and aroused from your sleep. You simply wrapped your arms around him, pulling him closer to you as you started to wake. Your hitched moans only driving him to move faster as his hip bones slammed into you rapidly.

“AH, Bl-Blue I’m gonna cuuuuumm!”

Sans eyes snapped to yours. His hand found your hair and he growled out, “Nngh Then do it, c-cum for me [y/n], cum for me.” His hips keep pistoning as he spoke. Before long, Sans felt your body tense up as an orgasm hit you like a freighter. Your back arched as you cried out his name. His hips never stopped moving as he rode it out. Before long he was soon pulled into it with you. Your walls clenched and milked him for all he was worth. He pressed kisses all over your chest and neck. Even left a bite mark on your shoulder.

You both laid there in the dark as your joined highs were coming down. Sans felt spent but happy as he took in your face. You looked sleepier than before, but yet you seemed to cling onto him. “You okay, Buttercup?” You nodded. Right now your mind was to busy trying to catch up with what just happened.

“Sans...I...did we…”

Sans kissed your head, “I kind of lost it there. You see, I just found out that you’re a sleepwalker apparently. Your magic is really potent stuff, by the way. Did you have a nice dream?”

"Kind of, I normally don't have-" As his words set in, you covered your face in embarrassment. “Nooo, I thought I got over that.”

Sans snickers, “This is a thing with you, how cute.”

“Shut up, I was a kid when this happened.” You shyly poke his nasal ridge. That doesn’t stop him from smiling his signature smile at you. “Ugh, you’re lucky I’m too tired to actually move.” You say flopping down on to the pillows, “which sucks because I’m sticky now.” The pout you displayed made the skeleton laying between your legs chuckle. The rumble of the laugh making your sensitive bits twitch.

“I CAN HELP WITH THAT.” Sans sits up easing his fading cock out of you. He pulls you into his arms and sits up. He brings you two out of the fort. “LET'S GET YOU CLEANED UP SHALL WE?” The cheeky grin growing on his lips made you suspicious.

You shrug and look at your sinnamon roll of a datemate’s face. “I feel like your planning something, again.”

“THE MAGNIFICENT SANS IS A CLEVER TACTICIAN AND AN OPPORTUNIST FOR SURE, BUT I ASSURE YOU THAT WAS NOT PLANNED.” his brow bone waggle in a playful manner.

“You’re so lucky you’re cute.” That’s all you say as you kiss his skull, “Now let’s get cleaned up so I can sleep. We have all weekend and I want a few more rounds before Papyrus gets home.” Sans and you take a moment to play in the shower before cleaning up and heading to bed. Let's just say that it was a weekend to remember. Also, that Papyrus got an interesting story from his brother.

His brother did tell him everything after all.

  
  
  
  


**Author's Note:**

> It's done. I hoped you like it. I had fun writing. Sure I pushed back homework to do so, but it is art and art requires sacrifice. Plus, I'm a procrastination queen. Just ask the dudes in my other stories. I take forever but the payoff is sweet when I do buckle down to get it done.
> 
> Anyway, That's all I got for ya my friends. See ya later. 
> 
> Buh-bye!!!


End file.
